.box{
    width: 100%;
    height: 100%;
    justify-content: space-between;
    display: flex;
}
.left{
    width: 200px;
    height: 100%;
    background-color: deepskyblue;
}
.center{
    flex: 1;
    background-color: #fff;
}
.right{
    width: 200px;
    height: 100%;background-color: hotpink;
}